Intravascular catheters, when inserted into a vein or artery, allow blood to flow back through the catheter under its own pressure. In some circumstances this flowback of blood is desirable; however, in others, particularly if uncontrolled, this flow-back and subsequent leaking of blood is inconvenient and even, in some cases, hazardous due to possible contamination of the operator and/or consequent infection of the host or other patients.
A common procedure used to introduce a plastic catheter is to include a sharp hollow needle within the bore of the catheter, which needle acts as a sharp introducer over which the catheter may be advanced into the blood vessel. When the sharp needle is inserted, blood flows rapidly back through the needle but is easily controlled at its proximal end. However, a problem arises when, the catheter having been advanced into the blood vessel, the sharp needle is withdrawn through the bore of the catheter thus allowing blood to flow freely through the catheter until the catheter is connected to other equipment incorporating a control device for the blood flow.
A common practice during this period between withdrawal of the needle and connection to equipment incorporating a blood flow control device is for the operator to palpate the vein into which the catheter is inserted at the skin surface immediately ahead of the catheter tip, thus compressing the vein and preventing or reducing blood flow. However, such a procedure is inconvenient in that it necessitates either multiple operators or a single operator manipulating the withdrawal of the needle and connection of the catheter to other equipment with one hand and, indeed, the procedure is not always feasible. A similar problem arises when a catheter is introduced through the bore of a needle or cannula, for instance a plastic tube, whereby the blood needs to be controlled in the same way.
Various attempts have been made to incorporate blood flow control devices in catheters such as, for example, valves, stopcocks and pieces of flexible tubing. However, such devices have not proved satisfactory. For example, even when open, their construction may result in impedance (resistance) to flow. Furthermore, valves tend to cause clotting of the blood, stopcocks are expensive and bulky, and pieces of flexible tubing are imprecise, cumbersome and add length to the catheter.
In addition, flow control devices with exposed operating means acting to compress an unsupported bore in the hub may result in the hazard of accidental closure of the bore and resultant halt in the administration of a therapeutic substance. Such accidental closure could be produced by strapping of the device, which is a common procedure for retaining an intravenous device in situ on a patient. Accidental pressure could also be applied by any firm surface against which the patient comes in contact. There is, therefore, a need for a catheter having flow control means which mitigate this hazard.